// SPDX-License-Identifier: GPL-2.0/* * llc_input.c - Minimal input path for LLC * * Copyright (c) 1997 by Procom Technology, Inc. * 		 2001-2003 by Arnaldo Carvalho de Melo <acme@conectiva.com.br> */#include <linux/netdevice.h>#include <linux/slab.h>#include <linux/export.h>#include <net/net_namespace.h>#include <net/llc.h>#include <net/llc_pdu.h>#include <net/llc_sap.h> #if 0#define dprintk(args...) printk(KERN_DEBUG args)#else#define dprintk(args...)#endif /* * Packet handler for the station, registerable because in the minimal * LLC core that is taking shape only the very minimal subset of LLC that * is needed for things like IPX, Appletalk, etc will stay, with all the * rest in the llc1 and llc2 modules. */static void (*llc_station_handler)(struct sk_buff *skb); /* * Packet handlers for LLC_DEST_SAP and LLC_DEST_CONN. */static void (*llc_type_handlers[2])(struct llc_sap *sap,				    struct sk_buff *skb); void llc_add_pack(int type, void (*handler)(struct llc_sap *sap,					    struct sk_buff *skb)){	smp_wmb(); /* ensure initialisation is complete before it's called */	if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)		llc_type_handlers[type - 1] = handler;} void llc_remove_pack(int type){	if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)		llc_type_handlers[type - 1] = NULL;	synchronize_net();} void llc_set_station_handler(void (*handler)(struct sk_buff *skb)){	/* Ensure initialisation is complete before it's called */	if (handler)		smp_wmb(); 	llc_station_handler = handler; 	if (!handler)		synchronize_net();} /** *	llc_pdu_type - returns which LLC component must handle for PDU *	@skb: input skb * *	This function returns which LLC component must handle this PDU. */static __inline__ int llc_pdu_type(struct sk_buff *skb){	int type = LLC_DEST_CONN; /* I-PDU or S-PDU type */	struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb); 	if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) != LLC_PDU_TYPE_U)		goto out;	switch (LLC_U_PDU_CMD(pdu)) {	case LLC_1_PDU_CMD_XID:	case LLC_1_PDU_CMD_UI:	case LLC_1_PDU_CMD_TEST:		type = LLC_DEST_SAP;		break;	case LLC_2_PDU_CMD_SABME:	case LLC_2_PDU_CMD_DISC:	case LLC_2_PDU_RSP_UA:	case LLC_2_PDU_RSP_DM:	case LLC_2_PDU_RSP_FRMR:		break;	default:		type = LLC_DEST_INVALID;		break;	}out:	return type;} /** *	llc_fixup_skb - initializes skb pointers *	@skb: This argument points to incoming skb * *	Initializes internal skb pointer to start of network layer by deriving *	length of LLC header; finds length of LLC control field in LLC header *	by looking at the two lowest-order bits of the first control field *	byte; field is either 3 or 4 bytes long. */static inline int llc_fixup_skb(struct sk_buff *skb){	u8 llc_len = 2;	struct llc_pdu_un *pdu; 	if (unlikely(!pskb_may_pull(skb, sizeof(*pdu))))		return 0; 	pdu = (struct llc_pdu_un *)skb->data;	if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) == LLC_PDU_TYPE_U)		llc_len = 1;	llc_len += 2; 	if (unlikely(!pskb_may_pull(skb, llc_len)))		return 0; 	skb_pull(skb, llc_len);	skb_reset_transport_header(skb);	if (skb->protocol == htons(ETH_P_802_2)) {		__be16 pdulen;		s32 data_size; 		if (skb->mac_len < ETH_HLEN)			return 0; 		pdulen = eth_hdr(skb)->h_proto;		data_size = ntohs(pdulen) - llc_len; 		if (data_size < 0 ||		    !pskb_may_pull(skb, data_size))			return 0;		if (unlikely(pskb_trim_rcsum(skb, data_size)))			return 0;	}	return 1;} /** *	llc_rcv - 802.2 entry point from net lower layers *	@skb: received pdu *	@dev: device that receive pdu *	@pt: packet type *	@orig_dev: the original receive net device * *	When the system receives a 802.2 frame this function is called. It *	checks SAP and connection of received pdu and passes frame to *	llc_{station,sap,conn}_rcv for sending to proper state machine. If *	the frame is related to a busy connection (a connection is sending *	data now), it queues this frame in the connection's backlog. */int llc_rcv(struct sk_buff *skb, struct net_device *dev,	    struct packet_type *pt, struct net_device *orig_dev){	struct llc_sap *sap;	struct llc_pdu_sn *pdu;	int dest;	int (*rcv)(struct sk_buff *, struct net_device *,		   struct packet_type *, struct net_device *);	void (*sta_handler)(struct sk_buff *skb);	void (*sap_handler)(struct llc_sap *sap, struct sk_buff *skb); 	/*	 * When the interface is in promisc. mode, drop all the crap that it	 * receives, do not try to analyse it.	 */	if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) {		dprintk("%s: PACKET_OTHERHOST\n", __func__);		goto drop;	}	skb = skb_share_check(skb, GFP_ATOMIC);	if (unlikely(!skb))		goto out;	if (unlikely(!llc_fixup_skb(skb)))		goto drop;	pdu = llc_pdu_sn_hdr(skb);	if (unlikely(!pdu->dsap)) /* NULL DSAP, refer to station */	       goto handle_station;	sap = llc_sap_find(pdu->dsap);	if (unlikely(!sap)) {/* unknown SAP */		dprintk("%s: llc_sap_find(%02X) failed!\n", __func__,			pdu->dsap);		goto drop;	}	/*	 * First the upper layer protocols that don't need the full	 * LLC functionality	 */	rcv = rcu_dereference(sap->rcv_func);	dest = llc_pdu_type(skb);	sap_handler = dest ? READ_ONCE(llc_type_handlers[dest - 1]) : NULL;	if (unlikely(!sap_handler)) {		if (rcv)			rcv(skb, dev, pt, orig_dev);		else			kfree_skb(skb);	} else {		if (rcv) {			struct sk_buff *cskb = skb_clone(skb, GFP_ATOMIC);			if (cskb)				rcv(cskb, dev, pt, orig_dev);		}		sap_handler(sap, skb);	}	llc_sap_put(sap);out:	return 0;drop:	kfree_skb(skb);	goto out;handle_station:	sta_handler = READ_ONCE(llc_station_handler);	if (!sta_handler)		goto drop;	sta_handler(skb);	goto out;} EXPORT_SYMBOL(llc_add_pack);EXPORT_SYMBOL(llc_remove_pack);EXPORT_SYMBOL(llc_set_station_handler);